Method of processing crustaceans

ABSTRACT

The invention relates to a method of processing crustaceans, live and cooked to cause detachment of shells from crustacean meat. According to the method, live crustaceans are exposed to hydrostatic pressure of relatively high value, for example between 20,000 p.s.i. to 60,000 p.s.i. for 2-5 minutes. The process is conducted at minimal elevated temperatures, in the range of above ambient temperature of 40 degrees to about 110 degrees Fahrenheit, leaving the raw crustacean meat substantially unaffected, in its desired raw state, while the connective tissue deteriorates and the shell detaches from the meat. As a result separating the edible meat from the shell becomes much easier and less time-consuming. Cooked crustacean meat can also be processed under hydrostatic high pressure in the order of 30,000 p.s.i. to 60,000 p.s.i. to eliminate or substantially reduce bacteria in the meat, thereby extending shelf life of the product.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of, and claims priority under 35 U.S.C. § 120 to,U.S. patent application Ser. No. 11/500,557, filed Aug. 8, 2006, whichis a continuation-in-part of copending nonprovisional application Ser.No. 09/121,725 filed on Jul. 24, 1998, the full disclosure of each ofwhich is incorporated by reference herein and priority of which ishereby claimed.

BACKGROUND OF THE INVENTION

This application relates to a method of processing seafood, and moreparticularly shellfish and crustaceans for the purpose of detachingshells from the meat and extending the shelf life of the edible meat.

Conventionally, crustaceans are cooked whole, either by exposure tosteam or boiling water, or by grilling. Whole crustaceans are alsopreserved by freezing prior to shipment to a customer. Anotherconventional method of processing crustaceans consists of cooking thecrustaceans and then cooling or freezing them individually, wrapped inwax paper. Still another method provides for the removal of the tailsections of lobsters, which sections are then quick-frozen and packagedin a box. However, frozen product tends to break during shipment, whichrenders the product less desirable to a consumer.

Some seafood processing plants prepare crustaceans for packaging byextracting meat from the body of the crustacean. It is well known thatthe crustacean meat is strongly attached to the shell and extractinguncooked meat is difficult, time consuming and often frustrating.Various mechanical devices are used for breaking the shell of acrustacean, including cracking devices, saws, and the like. Someprocessors cook the crustaceans and then hand-pick the prepared body toextract cooked meat, which is then packaged and refrigerated. One of theproblems associated with the latter method is a possibility of bacteriagrowth in the refrigerated product, which substantially reduces theshelf life of the product.

Irradiation (cold pasteurization) was tested as one of the methods ofdestroying harmful bacteria in shellfish and other food products.However, this process is relatively expensive and has not yet receivedconsumer support and confidence.

The present invention contemplates elimination of drawbacks associatedwith the prior art and reduction or elimination of harmful bacteria inshellfish, as well as cleaning of shellfish by high pressure processing.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide aprocess of processing of crustaceans and other shelled shellfish, suchas lobsters, crabs, crawfish and the like, to facilitate removal ofedible meat from the shell.

It is another object of the present invention to provide a method ofprocessing crustaceans, which causes detachment of the meat from theshell.

A further object of this invention is to provide a method of seafoodprocessing that allows to increase the shelf life of the product withoutadversely affecting the textural qualities of the product.

These and other objects of the present invention are achieved through aprovision of a process that includes hydrostatic high-pressure treatmentof shelled seafood, and particularly crustaceans, the process comprisingthe step of exposing the shelled product to relatively high hydrostaticpressure for a pre-determined period to cause detachment of the shellfrom the meat. The process is conducted at ambient temperatures, or withminimal heat, exposing the shelled product to liquid pressure of betweenabout 20,000 p.s.i. to about 60,000 p.s.i. for 2-5 minutes. Theprocessing is conducted at temperatures in the range from about 40degrees Fahrenheit to about 110 degrees Fahrenheit. The higher thetemperature, the less time and pressure is required to achievedetachment of the meat from the shell. As a result of high-pressureprocessing, the connective tissues of the crustaceans holding the shellwith the meat are denatured, and the shell can be removed from the meatwith minimal effort. The pre-determined elevated temperature can beachieved by heating the pressurized liquid in the pressure vessel or bydepositing warm water in the pressure vessel.

The instant invention also provides for a method of increasing the shelflife of a product, such as meat of a crustacean, by exposing the productto relatively high hydrostatic pressure for a pre-determined period tocause elimination of bacteria in the meat. The process is conducted atambient temperatures, or with minimal heat, exposing the shelled productto liquid pressure of between about 30,000 p.s.i. and about 60,000p.s.i. for 5-10 minutes. The processing is conducted at temperatures inthe range from about 40 degrees Fahrenheit to about 110 degreesFahrenheit.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the drawings, wherein

FIG. 1 is a schematic diagram illustrating correlation between heat,pressure and time factors in processing a crustacean, such as lobster tocause detachment of the shell from the meat.

FIG. 2 is a schematic diagram illustrating correlation between heat,pressure and time factors in processing a crustacean, such as crawfishto cause detachment of the shell from the meat.

FIG. 3 is a schematic diagram illustrating correlation between heat,pressure and time factors when processing crustacean meat, for instancecrab meat, for elimination of bacteria.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The new process for the treatment of raw shelled product according tothe present invention will now be described in more detail. According tothis process, the raw shelled product, such as crustacean, crab,crawfish and the like are treated in a high-pressure environment withminimal application of heat.

It is well known that shellfish, such as crab, crawfish and lobsterdeteriorate in quality immediately upon death. For this reason, one ofthe more expensive methods of introducing these products to the marketinvolves shipping the product either live in refrigerated containers, orfresh frozen. The consumer is then challenged to cook the fresh or freshfrozen product and hand pick the cooked product to extract edible meat.

According to the present invention, crustaceans, or other shellfish, areplaced in a pressure vessel that contains a pressure transmitting fluid,for example, water. If desired, the shellfish can be prepackaged inpouches and then loaded into the pressure vessel. The vessel is thenclosed and pressurized from between about 20,000 p.s.i. to 60,000 p.s.i.for 2-5 minutes at a temperature of between ambient temperature and 110degree Fahrenheit. The ambient temperature in this case is about 40degrees, or the temperature of refrigerated crustaceans shipped to aprocessing plant. It is the temperature at which the crustaceans aretypically processed at a processing plant. When the temperature iselevated, the pressure can be reduced as the combined effect of pressureand elevated temperature produces the desired result even at lowerpressure values in a shorter period of time. Elevated temperature may beachieved by depositing warm water in the pressure vessel.

For instance, during experimental tests, when fresh live lobsters wereprocessed in the pressure vessel at 60,000 p.s.i., and the temperaturewas elevated to 75 degrees Fahrenheit, it took only two minutes to causeshell detachment. At pressure of 50,000 p.s.i., at the same temperature,it took 3 minutes to cause shell detachment; at somewhat lower pressureof 40,000 p.s.i., at the same temperature of 75 degrees Fahrenheit, ittook about 4 minutes of processing to cause shell detachment; and atpressure of 30,000 p.s.i. at 75 degrees Fahrenheit, it took about 5minutes of processing to achieve the desired result.

FIG. 1 illustrates the correlation between time-pressure-temperaturefactors involved in the pressure processing of lobsters. The testsdemonstrated that one of the preferred methods of lobster processinginvolves pressurization up to 40,000 p.s.i. for 4 minutes at thetemperature of 75 degrees Fahrenheit. If it is desired to reduce thetreatment time, the pressure and temperature values have to beincreased. In such a case, the temperature range can be from ambienttemperature to as high as 110 degrees Fahrenheit and pressure up to60,000 p.s.i. If the temperature is elevated to 110 degrees Fahrenheit,the detachment of the shell can be achieved in 5 minutes when processingat 20,000 p.s.i. During experimental tests, the shells became detachedfrom the meat, leaving the meat intact, without any mechanical damage tothe meat.

The lobster body can be further processed by removing claws, tail andcracking the shell to easily remove intact pieces of edible meat. Theclean meat may be frozen until shipment to a customer. The lobster meatis not cooked; it remains fresh. The advantages of pressure processingalso include elimination of retaining tanks for shipping fresh lobsters.The meat yield is increased since the meat is intact. Frozen lobstermeat can be thawed and cooked according to conventional cooking methods.

During tests of processing shelled raw crawfish, as schematicallyillustrated in FIG. 2, it was also observed that the higher the pressureand temperature, the less time it takes to achieve the shell detachment.In the experimental tests, live fresh crawfish was processed in thepressure vessel filled with pressure-transmitting liquid, such as water.At 60,000 p.s.i., and the elevated temperature of 75 degrees Fahrenheit,it took only two minutes to cause shell detachment. At pressure of50,000 p.s.i., at the same temperature, it took 3 minutes to cause shelldetachment; at somewhat lower pressure of 40,000 p.s.i., at the sametemperature of 75 degrees Fahrenheit, it took about 4 minutes ofprocessing to cause shell detachment; and at pressure of 30,000 p.s.i.at 75 degrees Fahrenheit, it took about 5 minutes of processing toachieve the desired result. At the lowered pressure of 20,000 p.s.i. andhigh temperature of 110 degrees Fahrenheit, it takes about 5 minutes toachieve the shell detachment.

The post-pressurized crawfish can be further processed by removing theshell from the body and extracting the meat. After cleaning the meat, itcan be packaged, frozen and kept in a frozen state until furtherprocessing. The post-pressurized crawfish can also be packaged in ashell, frozen and stored for future processing.

The instant method of crawfish processing provides distinct advantagesin comparison with conventional methods. Conventionally, crawfish mustbe cooked shortly after harvesting. Even in a cooler, crawfish dieswithin two days. The short shelf life of this product creates problemsin storage, sales and distribution. Consumers are advised to remove deadcrawfish before cooking the rest of the batch.

When using the instant method of crawfish processing, a processor canship the product as packaged meat or in a shell, frozen whole to aretailer or distributor. The meat can be picked, packaged, frozen soldto a customer and cooked later, when convenient to a consumer. Since theproduct retains its fresh sensory characteristics, it can be cookedlater without sacrificing taste and texture.

Another problem that this invention solves is extending shelf life of aproduct, such as for instance crab meat. It is well known that crab meatis highly perishable. If not frozen or refrigerated, it spoils in amatter of days even when cooked. The instant method provides forpressure processing of crab meat to extend the shelf life of the productby killing bacteria that can lead to the product deterioration.According to the present invention, live crabs are cooked by exposingthem to steam or hot water immersion. The cooked crabs are then cooleduntil the temperature of the product is below 45 degrees Fahrenheit butthe crab body is not frozen. The cold crab bodies and claws are picked(meat separated from the shell). Then, claw meat is separated from thebody meat and packaged separately in plastic bags with or without apressure-transmitting liquid. The packaged crab meat is placed in apressure vessel and exposed to high pressure processing for apredetermined period of time to cause destruction of bacteria andreduction of bacteria count to a pasteurized level.

The present invention provides for a method of processing the meat of acrustacean by exposing the meat to hydrostatic pressure sufficient tocause elimination or substantial reduction of bacteria count. Thepressure is selected in the range of between 30,000 p.s.i. and 60,000p.s.i., temperature of between 40 degrees and 110 degrees Fahrenheit andtime of between 5 and 10 minutes.

Experimental tests conducted with packaged crab meat showed thatsignificant bacteria reduction was achieved in 5 minutes at 50,000p.s.i. and temperature of 75 degrees Fahrenheit. Favorable result wasalso achieved when processing at 40,000 p.s.i. for 10 minutes andtemperature of 75 degrees Fahrenheit. The same concept of pressure andtemperature discussed above applies to bacteria reduction, as well. Thehigher the temperature, the less time and less pressure is required toachieve the desired bacteria elimination and bacteria reduction. Thisstatement is reflected in the schematic illustration of FIG. 3.

The post-pressurized packaged product can be stored in a cooler at atemperature above freezing. The pressure-processed crab meat can bestored in a refrigerator up to six months. Other crustacean meat can besimilarly processed for long storage.

The present method of processing crustacean meat provides manyadvantages in comparison with conventional methods. Currently, in orderto achieve pasteurization, the product is heated. It is very difficultto achieve uniform heating throughout the package of cooked meat at thesame time. The temperature and time are very critical since too muchheat and/or time will overcook the meat; insufficient temperature and/ortime will not kill the bacteria. The cold pressure processing achievesuniform pressure distribution throughout the vessel and any productplaced in the pressure vessel. The time and temperature of processingcan be easily controlled, which makes this method more dependable andcommercially beneficial.

During processing for shell detachment or for bacteria elimination, thepressurized liquid remained at ambient or slightly elevated temperature,while the pressure was transmitted uniformly to the product inside thepressure vessel. It was determined that for every 1,000 ATM (14,500p.s.i.) of pressure increase, the temperature in the pressure vesselincreased by about 3 degrees Celsius. The temperature decreased as soonas the pressurization stopped. The resultant product did notsignificantly change in volume and no mechanical damage was observed tothe delicate food product. Some experiments showed that preferredpressures are in the range of 40,000 p.s.i.

During experiments with live crustaceans, it was observed that themuscle connective tissue attachment at the shell denatured to gelformation and the meat easily slides out of the shell in perfectcondition. No mechanical cutting is necessary. The denaturing of muscleproteins, including actin and myosin and connective tissues to a gelatintransition is believed to be a result of disruption of non-covalentinteractions in tertiary protein structures.

If desired, the crustacean claws may be banded before processing in thepressure vessel. The band may be a flexible band, such as a rubber band,or a plastic shrink tape. An external pressure source is used forsupplying pressure to the pressure chamber of the vessel, where thecrustaceans have been deposited. According to Pascal's Law, thishydrostatic pressure has a uniform effect on all materials inside thepressure vessel. Equally distributed pressure affects the edible meatinside the shells and causes detachment of the shell connective tissuewithout any mechanical damage to raw crustacean meat.

For lower pressures, the time of treatment and temperature are greater,while higher pressure requires less treatment time and less temperature.A slight increase in temperature would decrease the amount of pressurerequired. The connective tissue is disrupted and bacteria eliminated,while nutritional value and sensory qualities of raw crustacean meat orcooked crustacean meat are not affected.

If desired, live crustaceans can be processed for meat separation,opened at the processing plant, picked and the meat packaged in plasticbags. The packages are then pressurized at higher pressures to eliminatethe bacteria and extend the shelf life of the product. Also, variousspices and flavorings can be added to the pressurized fluid. Forexample, salt, lemon juice, hot spices and other flavor enhancingadditives may be deposited into the pressure vessel along with waterbefore pressurization begins. During pressure processing, the flavorenhancing substances penetrate into the raw product and make the productmore desirable to consumers.

The method in accordance with the present invention does not causethermal damage or denaturing of the delicate product as the temperatureincrease is minimal. At the same time, no mechanical damage to thedelicate meat occurs, as the shell or packaging protect the crustaceansand their meat from any contact with the mechanical parts of thepressure vessels.

The method of the present invention has minimal impact on theenvironment. Cooling water can be recycled through the use ofconventional equipment. Conventional electromechanical systems can beused to generate high pressure inside the pressure vessels withoutaffecting the advantages afforded through the practice of the presentinvention.

It is envisioned that various types of hard shelled crustaceans can beprocessed using the method of the present invention. By way of exampleand not of limitation, the instant method may be used for processing alltypes of lobsters and crabs, such as Irish crab, Snow crab, Stone crab,Alaska King crab, and Dungeness crab, crawfish and shrimp. Following thehigh pressure processing disclosed above, the shellfish remains in itsshell, with meat intact, loosened or detached from the shell. The meatretains sensory characteristics of raw product and increased shelf life.The processed product can be either cooled, packaged either shipped to acustomer intact, or further processed at a plant to remove the shell, asdiscussed above. The separated meat of the crustacean can be furthercooled, packed and shipped without the shell.

Many changes and modifications can be made in the process of thisinvention without departing from the spirit thereof. I, therefore, praythat my rights to this invention be limited only by the scope of theappended claims.

1. A method of extending shelf life of cooked seafood, comprising thesteps of: exposing cooked seafood to a predetermined hydrostaticpressure at a temperature from ambient to a predetermined elevatedtemperature for a predetermined period of time sufficient to causedestruction of the bacteria in said cooked seafood.
 2. A method ofextending shelf life of cooked meat of crustaceans, comprising the stepsof: exposing said cooked meat of crustaceans to predeterminedhydrostatic pressure of between about 30,000 p.s.i. and 60,000 p.s.i. ata temperature above ambient for a predetermined period of timesufficient to cause destruction of the bacteria in said cookedcrustacean meat.
 3. The method of claim 2, wherein said cookedcrustacean meat is packaged in liquid impermeable bags prior to exposingsaid crustacean meat to hydrostatic pressure.
 4. The method of claim 3,further comprising a step of: depositing a pressure transmitting liquidin said bags and sealing said bags prior to exposing the crustacean meatto hydrostatic pressure.
 5. The method of claim 2, wherein saidcrustacean meat is exposed to hydrostatic pressure for a period of timeof between 5 and 10 minutes.
 6. The method of claim 2, wherein saidcrustacean meat is exposed to hydrostatic pressure at a temperature fromabout 40 degrees Fahrenheit to about 110 degrees Fahrenheit.
 7. Themethod of claim 2, wherein said crustacean meat is exposed tohydrostatic pressure at a temperature of about 75 degrees Fahrenheit forabout 10 minutes.